I would like to add to this post everything I know about this situation; hopefully it'll be a compendium of info because I see so many bits and pieces scattered everywhere.
First off, the menu bar in earlier builds of Leopard was generated using transparency and blur. All cards that support Quartz Extreme, which is required for the blur, rendered the effect. Hardware-accelerated Core Image was not required.
In Build 9A581, the menu bar was generated using a Core Image recipe, making use of Quartz GL. The fall-back path renders the opaque menu bar for non-Quartz GL cards. The GFX 5200 is in that category according to Apple, though my understanding was, since it is programmable and supports pixel/vertex 2.0 shaders and ARB_fragment_program, that it is in fact capable of Quartz GL in hardware. At this point, I'm not sure what requirement the GFX 5200 really does not fulfill, though my guess is support for ARB_texture_non_power_of_two. Second, since the menu bar isn't redrawn when something is "slipped" underneath it, I'm not sure why the effect couldn't be rendered in software; I can't imagine it being too slow.
Apple's initial tech note said that all Core Image capable cards would render the effect. Also, an AppleCare rep I spoke to said the GFX 5200's rendering an opaque menu bar is a bug that would be addressed in 10.5.1.
On November 6, the tech note changed to specifically exclude the GFX 5200, for it "may" lack the necessary OpenGL capabilities. Yes, "may," a rather oblique word, if you ask me. I again called AppleCare, and this time the rep merely read that tech note to me.
Why did Apple change how the menu bar is generated? I'd say readability, but Apple could have simply increased the opacity in the developer builds, which had obnoxiously translucent menu bars. Or perhaps they could have <gasp> given users some control and let them adjust the translucence in System Preferences/Appearance. The reason must be, then, yet unrevealed, be it support for resolution independence or whatever.
I can say that Apple does not regard this as a bug. And yes, I know this isn't worth getting worked up about, but in principle, I feel as though I've been shorted of a promised selling point of Leopard. And yes, the effect strikes me as (currently) completely over-engineered. Another beef: I have a computer newer and more expensive than many that do the effect. Also, Apple should be more forthcoming about this: As it is, there are 7 computer SKUs that have a GFX 5200 that can't be upgraded, and what Steve Jobs said in his open letter to early iPhone adopters isn't here irrelevant, "Our early customers trusted us, and we must live up to that trust with our actions in moments like these."
In sum, I do not want the opaque menu bar, and I would at least like a "fall-back path" of an adjustably translucent menu bar, not unreasonable given Leopard's modular GUI design. And I'm more than happy to support a 3rd-party endeavor, but efforts at a compatibility patch don't look promising.
